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SHA2(3)                    Library Functions Manual                    SHA2(3)

     SHA224_Init, SHA224_Update, SHA224_Final, SHA224_Transform, SHA224_End,
     SHA224_File, SHA224_FileChunk, SHA224_Data, SHA256_Init, SHA256_Update,
     SHA256_Final, SHA256_Transform, SHA256_End, SHA256_File,
     SHA256_FileChunk, SHA256_Data, SHA384_Init, SHA384_Update, SHA384_Final,
     SHA384_Transform, SHA384_End, SHA384_File, SHA384_FileChunk, SHA384_Data,
     SHA512_Init, SHA512_Update, SHA512_Final, SHA512_Transform, SHA512_End,
     SHA512_File, SHA512_FileChunk, SHA512_Data - calculate the NIST Secure
     Hash Standard (version 2)

     #include <sys/types.h>
     #include <sha2.h>

     SHA224_Init(SHA224_CTX *context);

     SHA224_Update(SHA224_CTX *context, const uint8_t *data, size_t len);

     SHA224_Final(uint8_t digest[SHA224_DIGEST_LENGTH], SHA224_CTX *context);

     SHA224_Transform(uint32_t state[8],
         const uint8_t buffer[SHA224_BLOCK_LENGTH]);

     char *
     SHA224_End(SHA224_CTX *context, char *buf);

     char *
     SHA224_File(const char *filename, char *buf);

     char *
     SHA224_FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     SHA224_Data(uint8_t *data, size_t len, char *buf);

     SHA256_Init(SHA256_CTX *context);

     SHA256_Update(SHA256_CTX *context, const uint8_t *data, size_t len);

     SHA256_Final(uint8_t digest[SHA256_DIGEST_LENGTH], SHA256_CTX *context);

     SHA256_Transform(uint32_t state[8],
         const uint8_t buffer[SHA256_BLOCK_LENGTH]);

     char *
     SHA256_End(SHA256_CTX *context, char *buf);

     char *
     SHA256_File(const char *filename, char *buf);

     char *
     SHA256_FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     SHA256_Data(uint8_t *data, size_t len, char *buf);

     SHA384_Init(SHA384_CTX *context);

     SHA384_Update(SHA384_CTX *context, const uint8_t *data, size_t len);

     SHA384_Final(uint8_t digest[SHA384_DIGEST_LENGTH], SHA384_CTX *context);

     SHA384_Transform(uint64_t state[8],
         const uint8_t buffer[SHA384_BLOCK_LENGTH]);

     char *
     SHA384_End(SHA384_CTX *context, char *buf);

     char *
     SHA384_File(char *filename, char *buf);

     char *
     SHA384_FileChunk(char *filename, char *buf, off_t offset, off_t length);

     char *
     SHA384_Data(uint8_t *data, size_t len, char *buf);

     SHA512_Init(SHA512_CTX *context);

     SHA512_Update(SHA512_CTX *context, const uint8_t *data, size_t len);

     SHA512_Final(uint8_t digest[SHA512_DIGEST_LENGTH], SHA512_CTX *context);

     SHA512_Transform(uint64_t state[8],
         const uint8_t buffer[SHA512_BLOCK_LENGTH]);

     char *
     SHA512_End(SHA512_CTX *context, char *buf);

     char *
     SHA512_File(char *filename, char *buf);

     char *
     SHA512_FileChunk(char *filename, char *buf, off_t offset, off_t length);

     char *
     SHA512_Data(uint8_t *data, size_t len, char *buf);

     The SHA2 functions implement the NIST Secure Hash Standard, FIPS PUB
     180-2.  The SHA2 functions are used to generate a condensed
     representation of a message called a message digest, suitable for use as
     a digital signature.  There are four families of functions, with names
     corresponding to the number of bits in the resulting message digest.  The
     SHA-224 and SHA-256 functions are limited to processing a message of less
     than 2^64 bits as input.  The SHA-384 and SHA-512 functions can process a
     message of at most 2^128 - 1 bits as input.

     The SHA2 functions are considered to be more secure than the sha1(3)
     functions with which they share a similar interface.  The 224, 256, 384,
     and 512-bit versions of SHA2 share the same interface.  For brevity, only
     the 256-bit variants are described below.

     The SHA256_Init() function initializes a SHA256_CTX context for use with
     SHA256_Update(), and SHA256_Final().  The SHA256_Update() function adds
     data of length len to the SHA256_CTX specified by context.
     SHA256_Final() is called when all data has been added via SHA256_Update()
     and stores a message digest in the digest parameter.

     The SHA256_Transform() function is used by SHA256_Update() to hash
     512-bit blocks and forms the core of the algorithm.  Most programs should
     use the interface provided by SHA256_Init(), SHA256_Update(), and
     SHA256_Final() instead of calling SHA256_Transform() directly.

     The SHA256_End() function is a front end for SHA256_Final() which
     converts the digest into an ASCII representation of the digest in

     The SHA256_File() function calculates the digest for a file and returns
     the result via SHA256_End().  If SHA256_File() is unable to open the
     file, a NULL pointer is returned.

     SHA256_FileChunk() behaves like SHA256_File() but calculates the digest
     only for that portion of the file starting at offset and continuing for
     length bytes or until end of file is reached, whichever comes first.  A
     zero length can be specified to read until end of file.  A negative
     length or offset will be ignored.

     The SHA256_Data() function calculates the digest of an arbitrary string
     and returns the result via SHA256_End().

     For each of the SHA256_End(), SHA256_File(), SHA256_FileChunk(), and
     SHA256_Data() functions the buf parameter should either be a string large
     enough to hold the resulting digest (e.g., SHA224_DIGEST_STRING_LENGTH,
     SHA512_DIGEST_STRING_LENGTH, depending on the function being used) or a
     NULL pointer.  In the latter case, space will be dynamically allocated
     via malloc(3) and should be freed using free(3) when it is no longer

     The following code fragment will calculate the SHA-256 digest for the
     string "abc", which is

           SHA256_CTX ctx;
           uint8_t results[SHA256_DIGEST_LENGTH];
           char *buf;
           int n;

           buf = "abc";
           n = strlen(buf);
           SHA256_Update(&ctx, (uint8_t *)buf, n);
           SHA256_Final(results, &ctx);

           /* Print the digest as one long hex value */
           for (n = 0; n < SHA256_DIGEST_LENGTH; n++)
                   printf("%02x", results[n]);

     Alternately, the helper functions could be used in the following way:

           SHA256_CTX ctx;
           uint8_t output[SHA256_DIGEST_STRING_LENGTH];
           char *buf = "abc";

           printf("0x%s\n", SHA256_Data(buf, strlen(buf), output));

     cksum(1), md4(3), md5(3), rmd160(3), sha1(3)

     Secure Hash Standard, FIPS PUB 180-2.

     The SHA2 functions appeared in OpenBSD 3.4 and NetBSD 3.0.

     This implementation of the SHA functions was written by Aaron D. Gifford.

     The SHA256_End(), SHA256_File(), SHA256_FileChunk(), and SHA256_Data()
     helper functions are derived from code written by Poul-Henning Kamp.

     This implementation of the Secure Hash Standard has not been validated by
     NIST and as such is not in official compliance with the standard.

     If a message digest is to be copied to a multi-byte type (i.e.: an array
     of five 32-bit integers) it will be necessary to perform byte swapping on
     little endian machines such as the i386, alpha, and vax.

NetBSD 10.99                    October 9, 2018                   NetBSD 10.99